Control apparatus for reversible motors



y 1947- M. s. SHOEMAKER CONTROL APPARATUS FOR REVERSIBLE MOTORS FiledApril 28, 1944 firms/a4: Ma

Patented July 29, 1947 a. Shoemaker,

Allington. to l'hllco Corporation. Philadelphia, poration ofPennsylvania Pa aaaignor la..acor- Application April 28, 19, Serial No.533,188

Claim.

This invention relates to a novel system for controlling a reversiblemotor, and more particularly to novel means for effecting controlledperiodic reversal of the motor. The invention is particularly useful incontrol of an electric motor-driven mechanism, such as the scanningantenna employed in radio detecting and ranging (radar) systems and thelike,

In certain systems of this character, the scanning equipment is drivenby an electric motor which is, or may be, periodically reversed so thatthe scanning equipment is driven back and forth across a desired sector.In addition to this periodic reversal of the motor, means may beprovided to permit continuous rotation of the motor and hence continuousrotation of the scanning equipment. A system of this character isdisclosed and claimed in a copending application of Frederick R. Farrow,Jr., Serial No. 528,898, filed March 31, 1944. The present invention isin the nature of an improvement of that system.

In some applications of such systems, particularly in the case of ascanning antenna as mentioned above, certain advantages are to bederived from a system in which the continuous rotation of the motor ispossible only in one predetermined direction. For example, when someindicating device is associated with the scanning antenna the naturaland more easily followed direction of rotation of the indicator is theclockwise direction. Also, one particular direction of continuousrotation of the scanning antenna will usually produce the minimuminterference with the gyroscope which is frequently employed with thescanning antenna to maintain the effective axis of rotation of theantenna in some desired position.

It is, therefore, an object of the present invention to provide a simplecontrol arrangement for use with a motor-driven scanning device, bymeans of which the mode of operation of the scanning device may bechanged, at will, from a sector scanning mode of operation to a mode ofoperation involving continuous rotation in a predetermined sense ordirection. and vice versa.

Other objects and advantages of the invention will become apparentduring the course of the following description with reference to theaccompanying drawings, in which Fig. 1 is a d agrammatic illustration ofa typical control system embodying the principles of the invention;

F a. 2 is a plan view of an interlocking mechanism employed inaccordance with the present invention; and

2 Fig. 3 is a sectional view taken along line 3-3 of Fig. 2. 7

Referring to Fig. l, a reversible motor 2 is provided and arrangedcontinuously to rotate, or.

alternatively. to oscillate. a mechanism such as a directional antenna,or other device, over which control of rotation and period or amplitudeof oscillation is desired. In radar practice, structures of thischaracter are commonly known as spinners or scanning devices, and suchdevice is so designated in the drawing where it is representeddiagrammatically by the circular figure bearing the reference numeral 4.Since the structure and operation of such apparatus is known, and mayvary in detail according to the use to which it may be put, theparticular ap-' paratus driven by the motor 2 is neither specificallyillustrated nor described in detail herein,

The field winding 6 of the reversible motor 2 may be connected directlyto the supply line conductors l and III. The armature I! of this motoris connected to the same line conductors 8 and I0 through the agency ofthe conductors II and Hi, II and 10, and the reversing relay 22. Thereversing relay 22 is preferably of the over-center or latching" type.Reversing relays of this general character are well known in the art,and consequently it is deemed unnecessary to describe this device indetail. It will sumce to say that when the movable contactors 24 and 26are drawn to the right (as shown) by energization of the relay winding28 the said contactors will latch" in that position, and will remain inthat position until such time as the relay coil 30 is energized. At suchtime the contactors 2i and 28 will be drawn to the left, and will remainlatched in that position until such time as relay coil 20 is energized.It will be evident from the drawing that the movable contactors 24 and26, together with the fixed contact points 32, 34, 36 and 3! constitutea conventional reversing switch or relay. Thus, in one position of themovable contactors 24 and 16, the armature I! of the reversible motor 2is so connected to the line as to cause rotation of the motor in onedirection, while in the other position of the movable contactors 24' and26, the armature is so connected as to produce motor rotation in theopposite direction.

The armature or rotor I2 of the reversible motor may be mechanicallycoupled, by any suitable and convenient means, to the scanning device I.In the drawing, this mechanical coupling is represented by the dashedconnecting line. Also mechanically coupled to the reversible mo tor I,and rotating in synchronism with the scanning device 4, is a rotatingcommutator 4|, preferably constructed of a conducting material, andbearing a suitable contact element 42. Concentrically arranged aroundthe rotating commutator 40 are a plurality of fixed contact points, 46,4|, 5|, 52, and 54. These fixed contact points are preferably equallyspaced about the rotating commutator, and are so positioned with respectthereto that electrical contact is made between the said fixed contactpoints and the contact element 42 as the said element rotates past, orreaches, a given contact point. As shown in the drawing, the rotatingcommutator is connected by means of a conductor 5| to the conductor llof the line 8, In. The specific function of the rotating commutator 40will be described in detail hereinafter.

Each of the contact points 44, 4|, etc., are connected by means ofsuitable conductors to the similarly designated contact points of a pairof manually operable switches 58 and 6|. Thus, by way of example, thecontact point 44 associated with the rotating commutator 40 is connectedby way of the conductor 52 with the contact point 44a of the switch 50,and by way of the conductors 62 and 64 with the contact point 44b of theswitch 58. The switches 58 and 50 together comprise what may be referredto as a "sector selector, and they are so designated in the drawing.Preferably some interlocking means is provided between switches 58 and60 to revent switch arm 66 of switch 58 from occupying the same relativeposition as arm 58 of switch 60. The desirability of this will beexplained hereinafter and a preferred interlocking means will bedescribed.

At 90 in Fig. 1 there is schematically illustrated a three-circuitthree-position switch and, for explanatory purposes, the threepositions, namely On, Trip, Oil, of the rotatable member of the switchare separately shown. This switch may be referred to as the sectorscanning "On- Ofi switch. One circuit of switch 90 comprises contacts aand b, another circuit comprises contacts c and d and the third circuitcomprises contacts e and f. The rotatable member of the switch comprisesthe three segments u, v and w, of conducting material, suitably mountedand insulated from each other. For simplicity, specific connections tothe switch contacts are shown for only the On position. Also, it is tobe noted that although there are three electrical positions, On, Trip,Off, for switch 90, it is preferable that only two mechanical positions,namely, On and CE, be incorporated in the construction of the switch.

In the On, or sector-scanning, position of the switch 90, the adjustablecontact arm 56 of switch 58 is connected by way of conductor 10, onecircuit (contacts a and b) of the three-circuit switch l0. and conductorH to terminal 82 of the reversing relay coil 28. Similarly theadjustable contact arm 68 of switch 60 is connected by way of conductor12, one circuit (contacts c and d) oi. switch 90, and conductor 13 toterminal 18 of reversing relay coil 30. The third circuit of switchcomprising contacts e and j, is arranged so that one contact, e in Fig.1, is connected by conductor I02 to the same side of the supply lineconductors 8, it that is connected to the rotating commutator 40. Theother contact 1 is connected by the jumper connection I04 to contact d,as shown in Fig. 1, or, alternatively, to contact b. The other terminals84 and 80 of coils 2| and 30 are connected together by means ofconductor 14 and to the line conductor 8 by way of conductor 1|.

4 According y. one terminal of each reversing relay coils 2| and 3| isconnected permanently and directly to one side of line I, ll. l'orsector scanning, connection between the other terminals of the coils I|and II and the other side of the line is mad through the sector scanning"On-0i!" switch II, the sector selector switches II and and the rotatingcommutator 4|. Where continuous rotation of the scanning device 4 isdesired, the switch is employed in a manner to be described hereinafter.

The component parts and connections illustrated in Fig. 1 having nowbeen described, the operation of the system will now be set forth.assuming the sector scanning "On-On" switch II is in the "On" or sectorscanning position. Let us assume that it is desired to so operate thescanning device 4 that the sector 81 shall be continuously scanned. Asindicated, the limits of the sector 81 are defined by the referencechararcters 44c and 4|c. By means of the structure provided, suchoperation is secured by setting the contact arms H and of sectorselector switches 5| and to corresponding and similarly designatedswitch contact points.

Thus the contact arm may be adjusted tocontactthecontactpoint4|a,whilethe0ontact arm||isadiustedtoeontactthecontactpoint 44b. These switch adJustments areillustrated inthedrawing.1fnowthefield| ofthemotorlisconnectedinthepropersensetotheline conductors and i|, and this ismost conveniently determined by trial, the system will operate asfollows. Assume that at the instant represented in the drawing thescanning device 4 and the rotating commutator 4| are being drivensynchronously in a clockwise direction by the reversible motor I. Whenthe contact element 41 of the rotating commutator reaches the contactpoint 4|, a connection will be completed between the line conductor IIand the terminal ll of relay coil 3|. This connection includes theconductor 5|, the rotating commutator 4|, contact element 42, contactpoint 4|, conductor contact point 45a, switch arm conductor 12, contact0, segment 0, contact (I, and the conductor 1|. Since terminal of therelay coil flisalreadyconnectedtotheothersideofthe line by way of theconductors l4 and 1|, the coil II is now energised from the line, andconsequently th movable contactors 24 and 2| are moved from the positionillustrated to their lefthand position, where they make contact withstationary contacts 82 and respectively, thus reversin the connectionsbetween the armature II and the line conductors I and thereby reversingthe direction of rotation of the motor. The direction of rotation of thescanning device 4 and the rotating commutator 4| are, of course, alsoreversed. and consequently the rotating commutator 4| now proceeds torotate in a countor-clockwise direction. This it continues to do untilthe contact element 4! reaches and makes contact with contact point 44.When this occurs a connection is completed between the line conductor IIand terminal of relay coil 2|. This connection includes the conductor5|, the rotating commutator 4|, contact element 4!, contact point 44,the conductors and N, switch arm conductor 1|, contact a, segment u,contact b. and the conductor ll. Since the terminal |4 of relay coil 2|is already connected to line conductor by way of the conductors l4 andII, the coil 2| is energised and movable contactors I4 and 2| are movedfrom their left-hand position to the right-hand position shown. Thiseiiects a second reversal of the motor 2. whencethescanningdevicelandtherotatingoommutator 4| are also reversed andbegin rotation in the clockwise direction. The foregoing train of eventswill now repeat cyclically so long asthecontactamstlandllorthesectorselectos switches remain in the positionsshown.

Itwilinowbeevidentthatitispossihleto establish, on the sector selectorswitches ll and I, connections corresponding to desired sectwlimitsonthescanningdevicekandthustoeifeciz continuous scanning over adesired sector. For example, if it is desired to sector-scan the sector8s included within the sector limits 52c and c.itisonlynecessarytoadiusttheswitcharmlt to contact the contact point 2!:and to adjust the switch arm is to contact the contact point Ila. Largersectors may be scanned by adjusting theswitcharms and"tothecontactpoints corresponding to the limits or the desired sector.Where six contact points are provided. as in the illustration, thesmallest sector which can be scanned is a 60' sector. It smaller sectorsare desired it is, of course, necessary only to increase the number ofcontact points associated with the rotating commutator and with the twosector selector switches.

Although it will normally be desired to scan sectors of substantiallyless than 180, it may, under certain circumstances, be useful to scansectors of greater than 180. Such large sectors are as readily scannedwith the apparatus illustrated as are the smaller sectors. As hasalready been stated, with the specific adjustment illusstrated in thedrawing, sector scanning of the device 4 is effected over the sector 81.1!, now, the relative positions of the sector selector switches arereversed. i. e., if contact arm 66 is moved to contact to and contactarm 8| moved to a, the scanning device 4 will sector-scan the sector S3.It will be observed that the sector 8; has the same limits as the sector81, but that sector S: is the complement of sector 81.

The scanning apparatus of the drawing has been described, so far, onlywith reference to its operation as a sector scanning system. Aswasindicated at the outset, the system illustrated in the drawing is alsoadapted to effect continuous rotation, in one predetermined direction,of the scanning device 4. The selection of sector scanning or ofcontinuously rotation in one predetermined direction is accomplished, inaccordance with the present invention, by means of the sector scanning"On-Oil switch 90. As previously stated, sector scanning is effected byplacing switch 90 in the On" position whereby contacts a and b areconnected together by segment u and contacts and d are connected bysegment 0. In this position of switch ll contacts e and I are in an opencircuited relationship. In the description of switch 90 it was statedthat, although there are preferably but two operating positions for thisswitch, there are three electrical positions for switch 90. The switchmechanism is so arranged that in turning the switch from On to 011" orfrom Oil to On" the rotatable member of the switch passes through theintermediate or Trip position. For continuous rotation of the scanningdevice 4 the sector scanning On-Oi!" switch it is turned to the "Oi!"position. This operation of switch Oil momentarily places the movableelement of the switch in the Trip position indicated in Fig. 1. When thesegments u, v and w occupy the positions correspending to this "Trip"position, the continuity of the circuits from sector selector switchesll andfltothereversingrelaycoilsflandilis opened at contacts a and b andc and d of switch ll by movement of segments as aud o. Thus sectorselector switches II and I cannot now energize reversing relay coils 2|and SI. Also as switch 90. passes through this "Trip" position the sement in of switch OI connects contacts e and I together, therebyeffectively connecting terminal ll of coil 30 to conductor ll of lineconductors I. II and energizing coil 80 to place contactors 24 and 2' intheir left-hand position. Motor 2 will then rotate in the directioncorresponding to this position of contactors 24 and 26. If the directionof continuous rotation is to be in the reverse direction, changingJumper I from contact d to contact b will result in coil 2. beingenergised when switch 9. is turned from "On" to Oil." The contactors 24and 20 will then be drawn to their right-hand position and motor 2 willrun continuously in the corresponding direction.

Since the reversing relay 22 is of "over-center" or latching type, it isunnecessary to continuously excite either of the relay coils to keepcontactors 24 and 28 in position. Thus when switch ll reaches its "01!position, all three circuits of the switch are open circuited asindicated in the "Oif" position for switch .0 in Fig. i. This positionof switch prevents further excitation of the reverse relay coils 28 andIll.

To return to sector scanning, switch 90 may be turned back to its Onposition. Going through the Trip position again will, of course, have noeffect upon the reversing relay 22 since the contactors 2! and 26 arealready in the position determined by switch 90 as it previously sweptthrough the Trip" position. It is evident then that only two operatingpositions, namely "On" and "Oil," are required for a dial indicator forswitch 90.

When operating the system for sector scannin it is desirable to avoidsimultaneous excitation of both coils 28 and 30 of the reversing relay22. Accordingly, some interlocking means should preferably be providedbetween sector selector switches 58 and 60 such that switch arms 66 and68 cannot rest on corresponding switch contacts at the same time. Toprovide this interlocking feature, the switches 58 and 60 may be of theganged" type in which switch arms 68 and 68 are separately adjustable byindividual control knobs through a concentric drive shaft arrangement.The interlocking may be accomplished by means of a pin and arcuate slotconnection between the two control knobs, where. for example, a pin inone control knob travels in a slot in the other control knob. Aninterlocking means of this type is illustrated in Figs. 2 and 3, whichshow only those parts of the sector selector switch which embody theinterlocking means, since the sector selector switch itself may be aconventional twin switch structure arranged for concentric driveoperation.

Referring to these figures, a control knob I i for one of the switcharms of the sector selector switch has a pin it extending into a slot ilin the other switch arm control knob II. The control knobs ii and II aresuitably mounted on the concentric drive shaft mechanism ll of thesector selector switch. Element 2| represents a dial plate for theposition indication of control knobs ii and I1.

As shown in Fig. 2, the relative positions of the switch arms may beindicated by the pointers 7, 23 and 25 on the control knobs Hand I1; Theradial line sections on indicator plate 2| represent theradial locationsof an arbitrary number of switch contacts.

From the illustration it is evident that the length of slot I!determines the extent of relative motion between the two control knobsII and I1, and hence the extent of relative motion between the switcharms 08 and 68 of the sector selector switch. As shown in Fig. 2, thecontrol knob H is in its maximum counter-clockwise position with respectto control knob i1 due to pin I! engaging the end of slot II. Thecontrol knob ii may be moved clockwise relative to knob l'l until pin l3strikes the other end of slot II. In

either of these limiting positions there will be a relative distance ofone contact between the two pointers 23 and 25 or between the two switcharms of the switch to which the drive mechanism i9 is connected, thuspreventing both switch arms from occupying the same relative position.The control knobs H and i1, may, of course, be so adjusted that oneswitch arm may be placed on any desired contact while the other switcharm may rest on any other non-corresponding contact.

The pin and slot connection between the two knobs has the furtheradvantage that both of the switches may be set by manually moving knobii in one direction so as to seiTknob I1 and then moving knob ii in theopposite direction to set it. In similar manner both switches could beset by moving knob ll. Thus both switches may be set by grasping onlyone of the knobs and moving it in the manner indicated.

It will be apparent that the invention is not limited to the specificpurpose illustrated and described, but may be utilized in any instanceto effect continuous rotation in one predetermined direction of anadjustable periodic reversing motor driven equipment. It'will also beapparent that various modifications within the scope of my inventionwill occur to those-skilled in the art. Therefore, I do not limit it tothe specific form and arrangement of the apparatus diagrammaticallyillustrated in the drawings.

I claim:

1. In an apparatus forcontrolling sector scanning equipment, a drivingmotor, scanning equipment driven by said motor, rotary switching meansdriven by said motor synchronously with said scanning equipment,manually-settable selector switching means for determining the locationand amplitude of the sector to be scanned, means controlled by both ofsaid switching means to cause reversing of said motor automatically assaid scanning equipment reaches the limits of the scanned sector, amanually-operable switch for rendering the aforesaid switching meansinoperative at will to interrupt the sector scanning, and meanscontrolled by said manual switch for actuating said motor-reversingmeans so as to cause continuous operation of the motor in a singlepredetermined direction, thereby to actuate said scanning equipmentcontinuously in said direction.

2. In an apparatus for controlling sector scanning equipment, a drivingmotor, scanning equipment driven by said motor, rotary switching meansdriven by said motor synchronously with said scanning equipment,manually-settable selector switching means for determining the locationand amplitude of the sector to be scanned, an electrically-operablereversing switch controlled bv both of said switching means to causereversing of said motor automatically as said scanning equipment reachesthe limits or the scanned sector, a manually-operable switch forrendering theaioresaid switching means inoperative at will to interruptthe sector scanning, and means controlled by said manual switch foractuating said reversing switch so as to cause continuous operation ofthe motor in a single predetermined direction, thereby to actuate saidscanning equipment continuously in said direction.

3. In an apparatus for controlling sector scanning equipment, a drivingmotor, scanning equipment driven by said motor, rotary switching meansdriven by said motor synchronously with said scanning equipment,manually-settable selector switching means for determining the locationand amplitude of the sector to be scanned, an electrically-operablereversing switch controlled by both of said switching means to causereversing oi, said motor automatically as said scanning equipmentreaches the limits of the scanned sector, said reversing switchcomprising movable contact means and a pair of actuating coils formoving the contact means between two positions, the contact means beingadapted to remain in either position when actuated thereto, amanually-operable switch having on and on positions and adapted tocontrol the sector scanning, and means operable by said manual switchduring its movement from its on position to its oil position formomentarily energizing a predetermined one of said coils to causecontinuous operation of the motor in a single predetermined direction,thereby to actuate said scanning equipment continuously in saiddirection.

4. In an apparatus for controlling sector scanning'equipment, a drivingmotor, scanning equipment driven by said motor, rotary switching meansdriven by said motor synchronously with said scanning equipment, a pairof manually-settable selector switches for determining the location andamplitude of the sector to be scanned, the limits of the seztor beingdetermined by the respective settings of said selector switches,interlocking means for preventing said selector switches from being setin similar positions, and means controlled by the aforesaid switchingmeans and switches for reversing said motor automatically as saidscanning equipment reaches the limits of the scanned sector.

5. In an apparatus for controlling sector scanning equipment, a drivingmotor, scanning equipment driven by said motor, rotary switching meansdriven by said motor synchronously with said scanning equipment, a pairof manually-settable selector switches for determining the location andamplitude of the sector to be scanned, the limits of the sector beingdetermined by the respective settings of said selector switches,coaxially-related control knobs for said selector switches, a pin andslot connection between said knobs for preventing said selector switchesfrom being set in similar positions, and means controlled by theaforesaid switching means and switches for reversing said motorautomatically as said scanning equipment reaches the limits oi thescanned sector.

6. Apparatus for actuating a rotatable device back and forth through anyone of a plurality of predetermined sectors or for rotating said devicecontinuously in one predetermined direction,

comprising a reversible motor connected to said device to drive thesame, rotary switching means driven by said motor synchronously withsaid device, said switching means including a rotating contact and aplurality of fixed contacts engageable by said rotating contact, amanually-adjustable sector selector device having fixed contactscorresponding to those of said rotary switching means, and also havingrotatable contact means adapted to be placed in engagement with theassociated fixed contacts, electrically operable means for eflectingreversal of operation of said motor, circuit connections between saidrotary REFERENCES CITED The following references are of record in the afile of this patent:

UNITED STATES PATENTS Number Name Date 1,124,086 Whittingham et a1. Jan.5, 1915 1,141,154 Tatum June 1, 1915 1,514,881 Norman Nov. 11, 19241,792,296 Given Feb. 10, 1931 1,978,947 Johanson et a1. Oct. 30, 19341,318,779 Lum Oct. 14, 1919 1,919,525 Nogosek July 25, 1933 2,294,831Carson Sept. 1, 1942 2,312,178 Levison et al Feb. 23, 1943

